1. Field of the Invention
The present invention concerns a torsion damping device of the type having at least two coaxial parts, mounted rotatably in relation to one another, counter to elastic damping means generally interposed circumferentially between them. Such a torsion damping device can be applied to a friction clutch, notably for a motor vehicle. The invention more particularly concerns a friction device acting between the coaxial parts.
2. Description of the Prior Art
In a known torsion damping device one of the rotary parts carries a friction disc, designed to be fixed with respect to rotation to a first shaft, in practice a driving shaft, the crankshaft of the engine in the case of an application to a motor vehicle, whilst another of the said rotary parts has a hub by means of which it is designed to be fixed with respect to rotation to a second shaft, in practice a driven shaft, the input shaft of a gearbox in the case of such a motor vehicle.
In such an assembly, the use of at least three rotary coaxial parts, one of these comprising a hub disc, is also known.
The damping device acts between this rotary part and that fixed to the driving shaft. The delimitation of the angular movement between this rotary part and that fixed to the driven shaft is provided by engagement means of meshing with clearance. A sub-assembly for preliminary torsional damping is generally interposed between these latter two rotary parts.
The interposing of an axially acting friction device between two rotary coaxial parts is also known. Such a device generally comprises a friction washer, one active surface of which rubs against one of the rotary parts, and elastic loading means axially forcing the friction washer towards the rotary part whilst bearing on the other rotary part.
In the known device mentioned above with three coaxial parts, two friction devices of this type are generally disposed, one, corresponding to the damper, between the rotary part connected to the driving shaft and the hub disc, and the other, corresponding to the preliminary damper, between the rotary part connected to the driving shaft and the rotary part connected to the driven shaft.
These friction devices are generally in the vicinity of the hub, in a space left free around the latter, delimited circumferentially by elastic damping means.
Also housed in this space is the sub-assembly for preliminary torsional damping.
It is thus complicated to install in this space other active devices such as, for example, devices for damping the end-of-travel impacts of the means of meshing with clearance.